types: improve type safety in test mock surfaces (web, electron, mobile) (#4755)

Remove 218 `any` types across 5 test files (web themeMock, chatProtocol test, electron ipc test, mobile WebSocketManager test, mobile ChatScreen test). All edits are type-level -- no runtime behavior changed. Remaining `as unknown as` casts are load-bearing seams between partial mocks and real types.

Author: claude[bot]